1. Field of the invention
The present invention relates to a clutch having a damper spring in a power transmission apparatus of a vehicle. Specifically, the present invention relates to a structure for restraining resonance of the damper spring.
2. Background Art
As conventional technology, a clutch for power transmission in a motorcycle having a damper spring with a structure for restraining resonance of the damper spring is known. Such a device is disclosed in, for example, FIG. 9 of Japanese Unexamined Utility Model Publication No. 4-30337 .
In the above document, the clutch having a damper spring is a multiple disk friction clutch used in a power transmission apparatus of a motorcycle having an internal combustion engine. The clutch is provided with a primary driven gear to which torque of a crankshaft of the internal combustion engine is transmitted. A clutch outer is capable of being connected to and disconnected from a main shaft of a transmission via a friction plate, and a clutch center and a plurality of damper springs are arranged between the primary driven gear and the clutch outer at intervals in a peripheral direction.
The clutch is provided with a friction spring comprising a coned disc spring for restraining resonance of the damper springs produced based on a variation in the torque of the crankshaft. The friction spring is disposed between a clutch side plate and the primary driven gear, and is positioned on an inner side of the damper springs arranged in the peripheral direction. The friction spring presses the primary driven gear in an axial direction to thereby bring the primary driven gear into contact with the clutch outer Further, slidable contact faces among the primary driven gear, the clutch outer and a cam ring are disposed on an inner side of the damper springs.
According to the above conventional multiple disk friction clutch, torque of the crankshaft transmitted to the primary driven gear is transmitted to the clutch outer via the damper springs, and is further transmitted from the friction plate to the main shaft via the clutch center in connecting the clutch. The damper spring can be elongated and contracted between the primary driven gear and the clutch outer and, accordingly, a damping function prevents an abrupt torque change produced in connecting the clutch or the like from being transmitted to the clutch outer.
The torque variation of the crankshaft results in elongation and contraction of the damper spring, and when a frequency of the torque variation coincides with natural frequency of the damper spring, the damper spring is resonated. However, frictional torque by frictional force produced on the slidable contact faces, based on press force of the friction spring, is operated to hinder the primary driven gear from rotating relative to the clutch outer. The resonance is therefore restrained.
In order to restrain the resonance of the damper spring in this way, a frictional torque is required which has a magnitude determined by frictional force produced on the slidable contact faces, and a distance from an axis line of the main shaft. The axis line of the main shaft is a rotational center line of the primary driven gear to an operational point of the frictional force.
When the slidable contact faces are disposed on an inner side of the damper spring as in conventional devices, the distance from the axis line of the main shaft to the slidable contact faces is comparatively short and, accordingly, in order to provide the required frictional torque magnitude, the frictional force produced on the slidable contact faces must increase by increasing the press force by the spring force of the friction spring.
Disadvantageously, when the press force is increased, the large press force operates on the slidable contact faces of the primary driven gear and the clutch outer and, accordingly, in order to minimize wear caused by the press force at the slidable contact faces of the both members, a wear resistant surface treatment is required on both of the members. This treatment adds to the difficulty and cost of manufacture.
The present invention is in part addressed to overcoming the disadvantages of the conventional art. The present invention includes a clutch having a damper spring in which frictional torque for restraining resonance of a damper spring can be provided by small press force by a frictional spring. The clutch member is capable of being connected to and disconnected from a driven gear and a driven shaft.
A driven gear and driven shaft are transmitted a torque of a drive shaft. The driven gear is arranged coaxially and rotatably to the drive shaft, and a plurality of damper springs are relatively rotatable between the driven gear and the clutch member by being elongated and contracted.
A friction spring is arranged between the driven gear and the clutch member, and transmits the torque of the driven gear to the clutch member The friction spring is arranged at intervals along a periphery, and presses the driven gear in an axial direction to thereby bring the driven gear into contact with the clutch member or a member integrated to the clutch member.
The contact restrains resonance of the damper springs by a frictional force produced on slidable contact faces of the members, the friction spring and the slidable contact faces are disposed on an outer side of the damper springs.
The friction spring is disposed on the outer side of the damper springs arranged along the peripheral direction, and presses the driven gear to the clutch member or the member integrated to the clutch member in the axial direction. This pressing brings both members into contact with each other. The slidable contact faces formed by the contact are disposed on the outer side of the damper springs and therefore, the slidable contact faces producing the frictional force are disposed on the outer side of the damper springs, and are disposed at positions at which distances from the axis line of the driven shaft are larger than those of the slidable contact faces according to the conventional technology, in which the contact faces are disposed on the inner side of the damper springs.
As a result of the above configuration, the frictional force for providing required frictional torque for restraining resonance of the damper spring may be smaller than that in the conventional technology. Therefore, the spring force by the friction spring may be small.
Further, the press force of the driven gear exerted on the clutch member or the member integrated to the clutch member at the slidable contact faces becomes small. Accordingly, wear at the slidable contact faces is minimized and durability increased. Further, since wear is minimized, there is no need for a wear resistant surface treatment on the slidable contact faces. This reduces difficulty and cost of manufacture.
Because the slidable contact faces are disposed on the outer side of the damper springs, an area of the slidable contact faces can be made larger than an area of conventional slidable contact faces. Therefore, without enlarging a diameter of the driven gear and a diameter of the clutch member or the member integrated to the clutch member, pressure based on the press force of the driven gear exerted on the clutch member can be reduced. This reduces wear at the slidable contact faces.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.